Snow itself won't stop you, when the water is is so cold it starts to freeze up in the jets or on the glass, that is the time you have to wait for it to warm up a degree or two.
Often when it snows the actual temperature is up above freezing, or hovering around freezing and won't really affect you one way or the other.
Though at least with WFP you are not going to worry about the ladder slipping from under you
Watch out for the water freezing on the ground, the air temperature may be ok, but if the ground temp is low then you'll need to throw down some road salt on patios and paths and so on, or at least on areas where people are likely to be walking!
Ian